Image modulating systems, also known as light engines, comprising a housing including spatial light modulating devices or light valves are well known. A spatial light modulating housing may function either in a light transmissive mode, such as for LCD light modulators, or it may be a light reflective spatial light modulating device using DMD or LCD, e.g. LCOS, light modulators.
Image modulating systems comprising reflective spatial light modulating devices based on mirrors suffer less from heat generation than other schemes. However, heat is generated by both the electrical circuits and components, usually located at the back of the reflective spatial light modulating device, and also the incident light which can provide thermal energy in the form of light mainly to the front side of the spatial light modulating device. Some of the light is absorbed by the reflective spatial light modulating device on front side as well as some on back side and in the reflective elements.
Many attempts to dissipate or drain the heat way from a reflective spatial light modulating device have been made. As an example in U.S. Pat. No. 6,751,027B2, the heat is drained from the backside of the reflective spatial light modulating device by means of a thermally conductive stud. This stud contacts the backside of the reflective spatial light modulating device.
One possible alternative is to drain the heat away from the backside of a spatial light modulating device via a thermal path using thermal conductivity of several elements, whereas the front side of the device is provided with cooling air, to cool the front side using convective cooling. This however has the disadvantage that the air usually is contaminated with dust or smoke, which can be deposited on the optical surfaces and cause malfunctioning of the spatial light modulating device itself, or any optical elements located near the spatial light modulating device. Even more, as there is ideally very little space between the optical system, such as a prism system of the image modulating system and the spatial light modulating device, the air provided to the front side would not be able to flow easily over the front side to be cooled. This results in a low cooling efficiency.